The present invention relates to synchronization for communications in general and, in particular, to synchronization for mesh satellite communication networks.
In satellite communications, the distance between a satellite and ground terminal (e.g., a gateway or user terminal) may vary over time. Because of this variance, synchronization between a gateway and ground terminal may occur on an ongoing basis. In some implementations, a gateway may serve as the master, and the user terminals may use communications received from the gateway for synchronization. For example, each user terminal may receive one or more signals from a gateway and, based on a reception time from the gateway to the user terminal or other received information, identify start points for the transmission of frames to, or reception of frames from, the gateway.
In mesh satellite communications, user terminals may communicate with each other via “1-hop” (e.g., directly through the satellite, instead of satellite-gateway-satellite). However, with such mesh communications, there are certain instances when gateway-based synchronization schemes are inadequate. Traditional gateway-based synchronization may not be sufficient to set up timing for user terminal to user terminal mesh communication, as such schemes may not provide adequate timing information for the relevant link between each user terminal and the satellite (e.g., instead timing the gateway to user terminal links). It may, therefore, be desirable to identify novel synchronization techniques to address these timing issues in mesh communications systems wherein timing control is to some extent gateway-based.